Not defending Ondrusek, who I thought was disappointing last year, mostly late in the season.
But overall in three MLB seasons he has allowed 155 hits in 174.2 innings and has a 1.34 WHIP overall. (I like to see a reliever at around 1.3 WHIP or better.) He has a 15-7 W-L record and a 3.45 ERA. And, based on Shelton's article, last season he did well with inherited baserunners. Ondrusek allowed 1.1 homers per nine inning lifetime, which is not bad for a GABP pitcher.
His big issue, seems to me, is walks. His lifetime K rate is 6.1 per nine, his walk rate is 4.1, and the walk rate has gone in the wrong direction over time. His K rate isn't great, but not terrible either.
My point is that despite complaints about his stuff, and despite some unhappy peripherals, Ondrusek has a reasonable set of performance stats. Last season, one could argue that Logan was ok for most of the season and just had a terrible August-September.
I tend to agree that the Reds will have a hard time finding room for him on the roster and that two years for Logan is a surprise. But his performance measures have been pretty reasonable for a middle reliever and I don't think it's a ridiculous signing.